This application claims priority from Korean Patent Application No. 2003-14568, filed Mar. 8, 2003, the entire contents of which are herein incorporated by reference to the extent allowed by law.
1. Field of the Invention
The present invention relates to a diaphragm edge of a speaker, and more particularly, to a diaghragm edge of a speaker formed by compressing a material including silicon rubber and having an emboss portion on a front surface thereof so that sensitivity of sound is improved.
2. Description of the Related Art
A diaphragm edge of a speaker has largely two functions. One function is to smoothly respond to the movements of parts of a vibration system and a driving system and simultaneously accurately maintain the position of a diaphragm by preventing the diaphragm from moving in a lateral direction. The other function is to prevent a sound wave radiated from the diaphragm to the front side thereof and a sound wave having a reverse phase which is radiated to the rear side thereof from being mixed and offset.
The amplitude of the diaphragm is in inverse proportional to the square of a frequency. Thus, since a great amplitude appears in a lower sound range, the edge requires a mechanical linearity feature of a vibration direction. Also, the edge requires a high vibration absorption ability (an inner loss) to prevent sound generated from the edge due to resonance from exerting a bad influence upon performance of a speaker. Since the edge is coupled to the outer circumference of the diaphragm, a light one (a low density) like the diaphragm is required. To satisfy the required performance, various materials for the edge have been developed.
The types and features of materials for the edge which are generally used are shown below in Table 1.
TABLE 1NameMaterialFeatureCoating fabricCotton woven fabricDurabilityVery goodPolyester woven fabric +MechanicalBadrubberlinearity featurePolyurethane resinPriceVery badacryl resinFoamedPolyether baseDurabilityBadpolyurethanePolyester baseMechanicalVery goodrubberlinearity featurePriceMediocreElastomerStyrene, ButadieneDurabilityVery goodRubber thermoplasticMechanicalMediocreelastomerlinearity feature(polyurethane,PriceMediocrepolyester base)
Among the materials for the edge listed in Table 1, a coating fabric and foamed polyurethane rubber are most used. Although the foamed polyurethane rubber is slightly expensive than the coating fabric, it is relatively cheaper and exhibits a balanced performance so as to be widely used. In the present specification, the foamed polyurethane rubber is mainly introduced.
A foamed polyurethane rubber edge has a low density and a superior elasticity which are features of a foamed material. Since the thickness of the foamed polyurethane rubber edge can be increased assuming it has the same weight compared to other materials, the foamed polyurethane rubber edge has an appropriate strength and a great support ability. Furthermore, the foamed polyurethane rubber edge is flexible so that the inner loss is great.
The foamed polyurethane rubber is generally classified into two types, i.e., polyester base and a polyether base, according to the type of polyol which is a material thereof, which are different characteristics. Polyester based polyurethane rubber has a superior weatherability but has a inferior moisture resistance so that, when the polyester based polyurethane rubber meets moisture and heat, it is hydrolyzed. In contrast, polyether based polyurethane rubber has a superior moisture resistance but has an inferior weatherability so as to be deteriorated by an ultraviolet ray.
Other than the foamed polyurethane rubber, the conventional materials for a diaphragm edge have defects as shown in Table 1. To improve the defects, a diaphragm edge including silicon receives wide attention.
Silicon itself exhibits high heat resistance, high cold resistance, high chemical resistance, high oil resistance, and high water resistance so that it is widely recommended as a material for the diaphragm edge. For example, in terms of the heat resistance, since the silicon has a great combination energy, it can be continuously used at temperatures between 150° C.˜350° C. and with mechanical, electrical, and chemical stability. In terms of the cold resistance, since the silicon has an amorphous structure, it can be used at temperatures between −60° C.˜−110° C. Also, in terms of a non-toxic feature, since the silicon is a physically inactive material, it can be used in the environment where a possibility of a human contacting the same is high.
Thus, when a silicon diaphragm edge is manufactured by using silicon, the various advantageous features of silicon can be reflected in the diaphragm edge. The frequency characteristic of a speaker has the shape of a sort of a low frequency filter. FIG. 1A is a plot showing the frequency characteristic curve of sound output from a speaker using a foamed polyurethane rubber edge. FIG. 1B is a plot showing the frequency characteristic curve of sound output from a speaker using a sponge edge. FIG. 2 is a plot showing the frequency characteristic curve of sound output from a speaker using a silicon edge. In the frequency characteristic curve of the conventional speaker, as indicated by portions A and B of FIGS. 1A and 1B, the amplitude is suddenly decreased in a predetermined frequency range. Such amplitude reduction phenomenon is also shown in the case of using the silicon diaphragm edge exhibiting a superior performance as a diaphragm edge as shown in a portion C of FIG. 2.
In the frequency characteristic curve of a speaker, the phenomenon in which the amplitude is suddenly decreased and returned to the original amplitude makes one, who listens to sound from a speaker that is a sound source, feel sound unsmooth.
Thus, a method is needed, which can maintain the diaphragm edge's durability, heat resistance, cool resistance, and so on, even when the environment where a silicon material is used changes, and prevent sound quality from being deteriorated by a sudden change in the amplitude in the frequency characteristic curve.
Also, a material having a low density and flexibility is used for the diaphragm edge of a speaker to improve sensitivity of sound. When the speaker is used for a long time, the shape of the diaphragm edge may be deformed by the weight of parts, in particular, the diaphragm, of the speaker. When the shape of the diaphragm edge is deformed so as not to be returned to the original shape, the sensitivity of sound is deteriorated.